The Researching Of The Characteristic Of Chang2,Yan9+10's Oil Reservoir In Hanqu-Zhangtianqu Of Dingbian Area In Ordos Basin

Hanqu-Zhantianqu Oil Region which is the main exploration and development block of Shaanxi Yanchang Petroleum Group limited Co. located in the west of Shanbei Slope Belt in Ordos Basin and the oil-bearing layers are mainly member 2 of Yanchang formation and member 9+10 of Yanan formation. With geological, geochemical and geophysical approaches the structure, sedimentary microfacies, reservoir bed characters, oil reservoir characters and oil-gas-water geochemical characters are studied in depth in this paper and the following achievements are obtained.Based on the subtly stratigraphic correlation, combined with the facies signs of rock types and their characters, sedimentary textures and structures, paleontology and well logging, member 2 of Yanchang formation is confirmed being deltaic plain parfacies sediments and member 9+10 of Yanan formation being meandering river sediments. After the plane regularities of distribution of thickness of sandstone and the ratios of sand and mud being comprehensively studied, the plane regularities of distribution of microfacies of every formation is made certain.The results of container rock evaluation show that member 9+10 of Yanan formation developed in early diagenetic phase and the physical property of member 9 is worse and the textures of the container rocks are mainly III type (medium container rock) or IV type (worse container rock) with miniature holes and medium throats and that the physical property of the clastic rocks with bigger granularity in member 10 whose is type II (better) is better and that the clastic rocks in member 2 of Yanchang formation developed in early stage of later diagenetic phase and the container rock type is III type (medium container rock) with middle hole sand middle throats or miniature holes and middle- miniature throats and a small quantity of type II (batter container rock)The traps are mainly structure- lithology trap and lithologic trap. The regularities of distribution of oil reservoirs in member 9+10 of Yanan formation are controlled by paleophysiognomy and sand bodies and the oil saturation is controlled by structure, lithology and physical property. There is edge water and bottom water in oil reservoir and drive types are mainly edge- bottom drive types. No obvious edge water or bottom water is found in member 2 of Yanchang formation. The formation pressure is over saturation differential pressure and the oil reservoir pressure is all along over saturation differential pressure during development process with some certain of elastic energy and the drive type in member 2 of Yanchang oil reservoir is elasticity- dissolved-gas drive.Through in depth research on structure, sedimentary microfacies, container rock characters, oil reservoir characters and oil-gas-water geochemical characters, it is shows that controlling factors about oil &gas accumulation are tectonism, source rock quality, container rock characters, shut-off capacity of regional and local cap rocks and facies belt of high quality container rocks. Underlying high quality source rocks in member 7 of Yanchang formation reached the oil generating peak in early Cretaceous. The reservior , cap rock , trap , migration , conservation conditon of Chang 2 and Yan 9+10 in study area has been available, which is the key factors for flock hydrocarbon accumulation. Besides the above, oil reservoirs in member 9+10 of Yanan formation in Jurassic are controlled by vertical migration pathway generated by riverway downcutting.Comprehensive analysis shows that there are four types of accumulation models: upword subtle accumulation models under the regional tectonic background, structure-lithology accumulation models formed by the matching of nosing structure upper curtate and sand bodies, ladder accumulation models controlled by facies belts and tectogenetic movements,strata overlap oil accumulation models.